1. Field of the Invention
The invention relates to single control proportioning valves for liquids, such as hot and cold water and, more particularly, to pinch tube valves, wherein a control cam mechanism is disposed for engagement with a pair of valve tubes to control the degree of pinching of, and thereby the proportioning and flow rate through, the valve tubes.
2. Description of the Prior Art
In the past, external camming sleeves having an eccentric interior surface portion have been used to control both the rate of flow and the proportioning for single control proportioning valves for a faucet having two supply lines. For example, in U.S. Pat. No. 3,880,400, the interior surface of a camming sleeve is used to selectively engage rubber pads covering the inlet ports of a valve body of a two supply line valve to vary the flow from each supply line through the valve. Though this valve works well, the valve body is of an intricate structure and expensive to make and replace.
Additionally, valves having two simple resilient rubber tubes, each fluidly connected to a different supply line have also been used in single control valves. These valves include a rigid cam member with a cammed exterior surface disposed between two resilient tubes. The axis of the cam member is perpendicular to the axes of the tubes. The cam member has a cylindrical portion and an eccentric conical portion and is rotatably and axially slidably movable within an elongated valve cavity. When the cam member is completely retracted within the valve cavity, its cylindrical portion engages the valve tubes and completely pinches them off. As the cam member is withdrawn or extended from the cavity, the conical portion thereof passes between the valve tubes, allowing them to expand and permitting an increasing flow rate therethrough, proportional to the amount of extension of the cam member. As the cam member is rotated, the eccentric conical portion presses or pinches the two valve tubes different amounts, so as to control the proportioning therebetween.
Since the axes of the resilient tubes of this type valve are perpendicular to the axis of the cam member, a special faucet design for a kitchen faucet is needed to accommodate this valve. Also, the flows from the two lines first combine after exiting the outlets of the two tubes. Since the outlets of the two tubes are close to the faucet outlet, the two flows are only allowed to mix for a short time. This short mixing time may cause an undesired laminar type flow, wherein the flow exiting the faucet includes portions made nearly entirely of hot or cold water (assuming a hot water supply line is connected to one tube and a cold water supply is connected to the other tube).